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  Ares I solid rocket first stage (Page 1)

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Author Topic:   Ares I solid rocket first stage
Robert Pearlman
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posted 08-10-2007 04:31 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
NASA Awards First Stage Contract for Ares Rockets

NASA has signed a $1.8 billion contract with Alliant Techsystems, known as ATK, located near Brigham City, Utah, for the design, development, testing, and evaluation of the first stage of the Ares I and Ares V launch vehicles.

This contract continues work that began on April 17, 2006, and includes delivery of five ground static test motors, two ground vibration test articles and four flight test stages, including one for the Ares I-X test flight.

NASA awarded the cost-plus-award-fee contract to ATK on a sole-source basis. The contract performance period extends through Dec. 31, 2014. First stage boosters for operational missions will be purchased through a separate contract.

ATK and its subcontractors possess the unique engineering capabilities for successful design and development of the first stage of the Ares I crew launch vehicle. The current space shuttle solid rocket booster is the only solid rocket booster manufactured in the United States that possesses both the required capabilities and safety margins necessary for the launch of a human-rated exploration space vehicle. These solid rocket boosters consistently have proven their capabilities and demonstrated reliability needed for the human exploration missions.

The Ares I first stage will be a five-segment solid rocket booster based on the four-segment design used for the shuttle. The basic design will draw on current hardware, facilities and manufacturing equipment qualified for human-rated solid rocket boosters.

The first stage will incorporate modifications to the current booster that are unique to the Ares I architecture to meet higher performance and reliability requirements for the Ares vehicles. Modifications include the additional segment and new solid rocket booster components.

Ares I is an in-line, two-stage rocket that will transport the Orion crew exploration vehicle to low Earth orbit. Orion will accommodate as many as six astronauts. The first stage will consist of the five-segment solid rocket booster. The second, or upper, stage will consist of a J-2X liquid-oxygen, liquid-hydrogen engine, a new upper stage fuel tank and associated avionics.

Ares V will enable NASA to launch a variety of science and exploration payloads, as well as key components, needed to travel to the moon and later to Mars. Ares V, a heavy-lift launch vehicle, is currently projected to use five RS-68 liquid-oxygen, liquid-hydrogen engines mounted below a larger version of the shuttle's external tank and two five-segment, solid-propellant rocket boosters for the first stage. The upper stage will use the same J-2X engine as the Ares I.

The first stage is managed by NASA's Marshall Space Flight Center in Huntsville, Ala., for NASA's Constellation Program.

fabfivefreddy
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posted 08-13-2007 03:56 PM     Click Here to See the Profile for fabfivefreddy   Click Here to Email fabfivefreddy     Edit/Delete Message   Reply w/Quote
Will this give us a fireworks display as big as the Saturn V?

mjanovec
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posted 08-13-2007 04:31 PM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
Only if it blows up.

Think of a taller version of a shuttle SRB with a second stage and capsule on top.

Robert Pearlman
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posted 08-13-2007 04:38 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
It depends on your definition of big and to which rocket you are referring.

Ares I will stand approximately 330 feet tall and Ares V will top off at about 360 feet. In that regard, both will be closer in stature to the Saturn V's 363 feet of booster.

Ares I will use a five-segment solid rocket booster as its first stage, providing a 10 percent increase in thrust over the four segment version used currently to launch the space shuttle. In October 2003, ATK performed a test fire of a five-segment SRB:

Ares V's first stage will employ two five-segment SRBs with a cluster of five RS-68 liquid-fueled engines. The RS-68 is the largest existing liquid hydrogen / liquid oxygen engine. As a comparison, the Delta IV Heavy uses three RS-68s:

Ben
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posted 08-13-2007 05:01 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by fabfivefreddy:
Will this give us a fireworks display as big as the Saturn V?
It also depends on what you are asking. In terms of thrust, the Ares I is about half of the shuttle and Saturn V, while Ares V is much much more than the Saturn V. Ares V should be the most powerful rocket in history in terms of thrust.

As for takeoff speed (the main factor that made Saturn V the big one to see) I am not sure of the exact weight numbers but I believe both Ares will accelerate faster than the Saturn V and probably comparable to the shuttle.

Apollo Redux
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posted 08-23-2007 08:44 AM     Click Here to See the Profile for Apollo Redux   Click Here to Email Apollo Redux     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Ben:
In terms of thrust, the Ares I is about half of the shuttle and Saturn V, while Ares V is much much more than the Saturn V. Ares V should be the most powerful rocket in history in terms of thrust.
Not according to this article.

Then again, until it actually flies, we won't know for sure. In any event, for those of us who will never know the thrill of a "Moon Shot" in person, the Ares V will be pretty darn close.

Ben
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posted 08-23-2007 11:36 AM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
Astronautix is incorrect and has become quite unreliable in recent times. It says in the descriptive paragraph the correct thing, that Ares V will use five RS-68 engines. Then in the data section it says that the Ares V will use three SSMEs instead!

Ares V will indeed use five RS-68 engines from the Delta 4 family, each boasting a full thrust of 650,000 lbs at sea level. They scrapped plans to use the SSMEs.

robsouth
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posted 08-30-2007 07:52 AM     Click Here to See the Profile for robsouth     Edit/Delete Message   Reply w/Quote
Is it just me or does anyone else hate the idea of those awful SRB's being carried forward into the next generation of space programs?

Whoever thought of making them segmented needs their heads seeing to and whoever agreed to them actually being used is even worse.

It's a new program, design a new rocket that's not segmented and doesn't need O rings.

SpaceAholic
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posted 08-30-2007 07:53 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Am not a fan of solids on Ares either - the rational for segmentation is really to simplify the casting and transportation process (longer casts are more susceptible to damage); going solids was largely political/economic decision with a bit of corporate nepotism thrown in and predicated little on technical merit.

cspg
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posted 08-31-2007 01:01 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
I'm not a fan of solid rockets either but I'm even more concerned about their re-usability (stress on the metal casings is worrisome).

As to developing a whole new launcher, it would also mean developing a new launch infrastructure. Is there enough money for both?

Jay Chladek
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posted 08-31-2007 06:26 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
I've thought about the solids, and I don't have a real problem with it. One thing you won't see on either the Ares 1 or V is the twang effect that the shuttle sees after SSME ignition, since Ares 1 doesn't have any liquid engines to fire on the pad and Ares V won't have them offset to the SRBs. So the segment rings on the SRBs won't see potential side stresses from that like shuttle does.

Ares 1 will have the LAS, so if a solid does cook off, the crew has a way out. It won't matter with Ares V, since that will be an unmanned HLLV anyway. But even then, failure of the SRB aft field joint on STS-51L not withstanding, the Shuttle SRBs have had a great performance and safety record. Granted there have been some issues, but the solids are a pretty well understood piece of engineering.

Even Arianespace is using segmented SRBs to my knowledge for their Ariane V booster. I also seem to recall the Air Force Titan III boosters were also segmented. Segmented SRBs are by no means unique to the shuttle program, or Ares.

Blackarrow
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posted 08-31-2007 06:54 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
One further safety plus point: on the shuttle, there are 2 SRBs. If one ignites and the other doesn't, it's curtains for the crew and the vehicle. On Ares 1, if the SRB doesn't ignite, the vehicle stays on the pad. Red faces, but no disaster.

SpaceAholic
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posted 08-31-2007 09:23 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Jay Chladek:
Segmented SRBs are by no means unique to the shuttle program, or Ares.
How many manned rated missions are you aware of that have relied exclusively on solids for any portion of their launch profile in the past (I know of none )...If solids fail its almost always catastrophic, they are not throttable and the segments are going to have to be pre-cast for a given mission many months/years prior to flight so that portion of the flight profile would be effectively "locked" and unalterable...and then you have the issue of this very high CG with a large mass atop of a long thin flexible tube (attitude control and low resonant frequency will probably make for very restrictive launch critera). The single Ares 1 solid is also an unmitigatable single point of failure - loss mandates compulsory and immediate bailout - Not a particularly transformational design in my view.

Jay Chladek
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posted 09-01-2007 11:49 PM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
True, the other solids out there are indeed not man rated, although if Ariane V were flying Hermes then I imagine it would have been man rated and I'm sure some design elements of the Ariane V boosters were probably drawn up for those reasons. In the case of Titan III, don't forget the Air Force was planning to use it for MOL, which would have been another manned application of a solid booster in a space program, if it had flown. At least in the case of the Titan III, they did send up a Gemini capsule and an MOL mockup on an unmanned mission (one step to man rating a system).

As for single point failure, yes there is that with the first stage of Ares, but that is splitting a hair. The reason I say that is although Shuttle doesn't use the SRBs exclusively, they are by and large the biggest producers of thrust. If anything, shuttle has a worse stage one profile then Orion. If the SSMEs shut down at launch and by some fluke the SRBs fire, then that stack isn't going very far is it will likely lean into the shuttle from the side loads and crash downrange (assuming the RSO doesn't destruct the vehicle at that point). With an SRB not firing, it is a worse situation. Wouldn't the failure of an SRB on shuttle be classified as a "single point" failure? There is certainly no backup for them.

Plus shuttle does not have a bailout option during first stage firing. The shuttle can't come off the tank fast enough if something happens, and it has been suggested in sim studies that if the crew tried to do a fast jettison, the orbiter would hang on the aft struts, pitch up nose first on the aft struts and then get ripped apart by the supersonic slipstream ala Challenger (assuming catastrophe from a solid that caused the abort didn't occur already). The difference here though is that the crew on Orion can abort safely.

Stage 1 failures tend to be catastrophic no matter whether they are solid or liquid powered. The recent Russian R-7 rocket failure with the Foton M-1 satellite comes to mind as it went up a few hundred feet, quit, then came back down in spectacular fashion. Probably the only one that wasn't catastrophic was the Gemini 6A pad abort. Even in that case, both engines on a liquid rocket stage shut down, not just one. The only manned booster I am aware of that might have had a decent chance to still get a spacecraft into orbit with an engine or two shut down on stage 1 would be the Saturn 1B, only because it had so many engines powering the first stage.

hlbjr
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posted 09-07-2007 12:37 PM     Click Here to See the Profile for hlbjr   Click Here to Email hlbjr     Edit/Delete Message   Reply w/Quote
Interesting comment on the 51L joint leak. Do you realize that would possibly be a relatively minor event with Ares 1 as there would not be a LOX/LH tank to explode which caused the failure of 51L? Instead, there may be a relatively minor thrust decay which may lead to less than optimal velocity and altitude at staging but that's about it. Maybe the 2nd stage could make up the shortfall, maybe not, but in my mind most 51L type SRB case-leak scenarios point to a non-life threatening outcome and possibly a continuation of the mission.

SpaceAholic
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posted 09-07-2007 02:08 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
The effects of hot blow by on Ares-1 would not be completely analogous to an SRB...lateral forces imparted on Ares from propulsive venting of the propellant gases would not be inconsequential. The shorter SRB's (which did not have to contend with a heavy payload mounted atop their structure) have higher rated aerodynamic loads then Ares/Orion.

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posted 09-07-2007 05:59 PM     Click Here to See the Profile for Danno   Click Here to Email Danno     Edit/Delete Message   Reply w/Quote
I think the first stage solid is a terrible idea. They should have man rated the EELVs which would be cheaper and quicker. But they weren't looking for a system or plan with technical merit.

art540
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posted 09-07-2007 11:11 PM     Click Here to See the Profile for art540   Click Here to Email art540     Edit/Delete Message   Reply w/Quote
What about upper level winds acting on the "sail" of the upper stage assembly? What about sea level winds on the exposed structure prior to launch? Will criterions be different from other vehicles?

robsouth
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posted 09-08-2007 09:34 AM     Click Here to See the Profile for robsouth     Edit/Delete Message   Reply w/Quote
This topic has made me realise just what a huge risk the shuttle crews take at SRB ignition, if onlyone fires it really is a bad situation.

Some of the points raised also makes me realise that A 51L situation wouldn't really happen on the new program because any escaping plume wouldn't be directly onto a huge tank of fuel.

Jay Chladek
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posted 09-10-2007 12:21 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
Upper level winds probably won't be as big a concern with Ares 1 as they are with big wide rockets like shuttle and Ares V. By comparison, look at Ariane IV and V. Ariane IV was a slim rocket compared to Ariane V and it caused a bit of a problem when CNES tried to use the same guidance system on Ariane V as they did on Ariane IV without modifications.

Without going into too much detail (because I don't remember all of it and I don't have the article I read about it), the first Ariane V was lost due to the INS system failing when the stack got this huge side gust of upper level winds. The secondary mode of the INS, which measures in small units as it takes readings of the final positioning of the booster on the pad prior to launch, was left on since that procedure didn't cause problems on Ariane IV. But this time the side gust put such a big deviation number in the system that it couldn't calculate it. It was like a calculator coming up "E" on the screen. So the system shut down and so did the backup, resulting in the flight going out of control and having to be terminated. The worst bit is when EADS (the contractor) ran the numbers in simulators after the fact, they found out the failure was inevitable.

Ares 1 is slim, but sim and testing data will reveal what its wind tolerances will be and those will be accounted for it its "Go/No Go" launch criteria.

Scott
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posted 09-14-2007 08:53 AM     Click Here to See the Profile for Scott   Click Here to Email Scott     Edit/Delete Message   Reply w/Quote
I am impressed - you guys really know your stuff.

I am curious about something and wanted to ask: Won't this single SRB design provide an exceptionally shaky ride? I know from viewing some cockpit videos of Shuttle launches that the SRBs cause most of the vibration (most of the vibration in the cockpit starts when the SRBs ignite and dissipates dramatically when the SRBs are jettisoned). It seems like a single SRB would provide a rough ride.

Jay Chladek
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posted 09-14-2007 01:53 PM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
That is a good question.I will be curious to find out myself. If there are, it shouldn't be any worse then a shuttle liftoff though.

My concern when I first heard about this configuration was the Gee forces on ascent as this skinny thing will probably climb a bit faster then a space shuttle. The vehicle I am guessing probably won't exceed three gees, but it will probably be a longer duration of three gees since according to what I have read about Shuttle ascents, they don't feel the heaviest Gee forces until late in the ascent when the External Tank is the lightest.

rocket ron
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posted 09-14-2007 05:51 PM     Click Here to See the Profile for rocket ron   Click Here to Email rocket ron     Edit/Delete Message   Reply w/Quote
Hoping to be involved with some part of that project. I left Boeing Satelite Design Center after ten years service and just started with ATK Space Systems.

robsouth
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posted 09-22-2007 11:40 PM     Click Here to See the Profile for robsouth     Edit/Delete Message   Reply w/Quote
I wonder if it will cause more vibration than a Saturn V launch. Has anyone else seen the FTETTM episode for Apollo 9? The interior of the LM is shown during liftoff and that suffers a fair bit of vibration.

cspg
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posted 11-07-2007 09:10 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
FlightGlobal.com: NASA admits "significant threats to performance" of Ares I launcher
The Ares I programme has been dogged by rumours of inadequate performance and blamed for repeated redesigns of the Orion's crew and service modules driven by the need to reduce mass. NASA has refuted the rumours and maintained that the Ares I CLV is capable of meeting requirements.

But now the agency's November internal circular says: "There are significant threats to the performance to be worked as the project works towards [PDR]."

Jay Chladek
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posted 11-07-2007 09:27 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
This reminds me of the old days of the Saturn Apollo program as written about in books I've read. The concerns are all the same, weight and capability. Granted Orion isn't going to the moon yet, but we have the same deal of one or two items gobbling up the weight and forcing some creative solutions to compensate for it. So I am a little worried to read about this, but it isn't time to throw in the towel just yet.

The only thing I don't like is that they seem to be cutting some of those features that would have helped the operational costs of Orion, such as apparently deleting the land landing capability. Meaning that the U.S. Navy will probably have to be "rented" for each recovery and the spacecraft will have to be cleaned of salt water after each flight (unless they plan to land in a lake). That may ease the development burden a little, but it is going to be a big cash register "Cha-Ching" for operational costs.

cspg
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posted 11-20-2007 12:27 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Jay Chladek:
I've thought about the solids, and I don't have a real problem with it.
Yet, during the Shuttle development, and I quote: "But a dual 156-inch-diameter SRB configuration was much more economical and held great promise, although the use of solids was disliked, and discouraged, by MSFC." (p373) Further, "It was a decision nobody liked, but it was the only one anybody could afford." (p376). Both quotes taken from "To Reach the high frontier", Ch.9 Broken in Midstride by R.Launius/D.Jenkins, editors.

I'm wondering if the reasoning still applies (budget) and if the people at MSFC back then still feel the same way, 35 years later...

SpaceAholic
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posted 01-18-2008 08:34 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Supplemental to earlier discussion on this thread pertaining to problems with using the solid first stage: NASA Moon Rocket May Shake Too Much

cspg
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posted 01-19-2008 12:33 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
I know that the argument for using solids is to keep the production line open for such
motors (amongst other things) but when you look at NASA's Orion spacecraft with a planned 22.7 metric tons mass (trimmed down somewhat lately?) and the launch capacity of the Delta IV Heavy (23 tons), I wonder what would be the resulting costs of man-rating the Delta, a booster that is flying...today.

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posted 01-22-2008 04:07 PM     Click Here to See the Profile for rocketJoe   Click Here to Email rocketJoe     Edit/Delete Message   Reply w/Quote
New York Times: New Rocket Has Problem With Vibrations
Engineers are concerned that a new rocket, the Ares I, which will replace the space shuttle and send astronauts on their way to the moon, could shake violently during the first minutes of flight.

The problem is common to solid rocket boosters.

If not corrected, the shaking, which arises from the powerful first stage of the rocket, could "shake apart the whole structure," said Paul Fischbeck, an engineering professor at Carnegie Mellon University.

Does anyone know why this would be a problem with Ares, and not currently an issue with the Space Shuttle? Is it because the SRBs are side mounted to the external tank thereby offering more stability?

art540
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posted 01-22-2008 07:52 PM     Click Here to See the Profile for art540   Click Here to Email art540     Edit/Delete Message   Reply w/Quote
Probably the mass and propellant absorption of the External Tank help to dampen any vibrations.

SpaceAholic
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posted 01-22-2008 08:13 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Speculative reply:

The short answer is different resonant frequencies (the Ares has a lower frequency which has a higher potential of matching the thrust oscillations from the solid) - The Ares vibration issue is exacerbated by low resonance of the launch vehicle which is partially an artifact of the multi-segmented design of the solid itself (the joint are in effect resonant cavities which compress and expand during flight). I believe the Shuttle SRB's have similar thrust oscillation problem but the overall resonant frequency of the Shuttle/ET is higher and less likely to amplify the oscillations.

KSCartist
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posted 01-23-2008 07:15 AM     Click Here to See the Profile for KSCartist   Click Here to Email KSCartist     Edit/Delete Message   Reply w/Quote
I'll be the first to admit I'm not a rocket scientist. So...

I've spoken to friends who work at KSC and Huntsville and this has been on there radar for some time. In fact one of them said that the Atlas V is under consideration to boost the Orion CSM into orbit.

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posted 01-23-2008 12:04 PM     Click Here to See the Profile for rocketJoe   Click Here to Email rocketJoe     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by KSCartist:
In fact one of them said that the Atlas V is under consideration to boost the Orion CSM into orbit.

It would be impressive to have the Atlas name boosting manned missions again!

Robert Pearlman
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posted 01-24-2008 03:09 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
On Tuesday, Jan. 22, NASA Administrator Mike Griffin gave a speech to the Space Transportation Association defending the Ares architecture and outlining why he/NASA believes that ELVs (such as Atlas) cannot be used to launch Orion.

A transcript of his remarks (PDF) is available.

During a Q&A session that followed, Griffin said of the oscillation problems raised earlier in this thread, "I think I have rarely seen more of a mountain made out of less of a molehill than this particular technical issue."

SpacePolitics.com has a summary of his reply.

Robert Pearlman
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posted 02-07-2008 01:02 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by KSCartist:
In fact one of them said that the Atlas V is under consideration to boost the Orion CSM into orbit.
NASA Administrator Mike Griffin pretty much squashes this rumor in an interview today with CBS/Spaceflight Now's Bill Harwood:
Let me get down to the bottom of it. There were winners and losers in the contractor community as to who was going to get to do what on the next system post shuttle. And we didn't pick (Lockheed Martin's) Atlas 5, in consultation with the Air Force for that matter, because it wasn't the right vehicle for the lunar job. Obviously, we did pick others. So people who didn't get picked see an opportunity to throw the issue into controversy and maybe have it come out their way.

In point of fact, the thrust oscillation, as it's called, on Ares 1 is not a significant problem and to the extent that it needs solutions, we've got three or four ways to go after it. We can put damping mechanisms between the first and second stage, beteween the second stage and Orion or within Orion itself to locally isolate things. This is something that's done on almost all of our unmanned vehicles, they have solid strap-ons and this thrust oscillation issue is one of the vibration drivers on most satellite vehicles and the satellites designed to fly on them have damping and isolation devices at the frequencies of interest, and that's what we'll do here.

I think you have been around long enough to know technically this is just not a big deal. It's about winners and losers. In the larger context, it's about winners and losers and people seeing an opportunity to reclaim a share of the pie that was lost. And I hate it when it comes to that. But that's it. The fact of the matter is, Ares, the rocket, and Constellation, the program, are designed to go to the moon and to provide a capability, if necessary, to service the space station in Earth orbit.

The Atlas 5 needs substantial upgrades in order to be a useful part of the lunar architecture and those upgrades, when we added them all up, cost more than the Ares 1. It's that simple. Now if you just want to go to low-Earth orbit and nowhere else, then the Atlas 5 will do just fine. And I encourage its use for that. What I don't encourage is for people to say that going to low-Earth orbit and stopping there again is a good goal. That's not what we're trying to do. We're trying to get back to the moon and we want to go on to Mars. And that needs something bigger.

cspg
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posted 02-19-2008 04:42 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
NASA Insists It Can Fix Flaw in Rocket Design (New York Times)
With a solid fuel rocket, the fuel starts burning at the bottom and combusts toward the top.
Really? I thought that in order to prevent hot gases to burn through the metal casing, fuel needs to burn at the same pace all along the booster's length (if not it's Challenger again)... am I wrong?

SpaceAholic
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From: Sierra Vista, Arizona
Registered: Nov 1999

posted 02-19-2008 06:42 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
In the case of the SRB the propellant grains generally burn along the length of the booster however not at a uniform rate. The grain pattern in the upper segments are cast (in an 11 point star pattern) so they burn at a slower rate which reduces thrust through Max-Q. The net result is that the lower segments of the SRB expend their propellant first.

cspg
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From: Geneva, Switzerland
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posted 02-19-2008 09:50 AM     Click Here to See the Profile for cspg   Click Here to Email cspg     Edit/Delete Message   Reply w/Quote
OI thought that all SRB segments looked like the one described on this page.

Robert Pearlman
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From: Houston, TX
Registered: Nov 1999

posted 02-28-2008 04:38 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From a presentation by Steve Cook, Ares Program Manager delivered Feb. 26 at the 3rd Space Exploration Conference.


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